Phase locked loops are used in a wide variety of applications. For example, phase locked loops are routinely used in communication devices to provide clock signals to various components of the devices. A conventional phase locked loop includes a charge pump that controls a reference voltage used by an oscillator to produce an output signal. Conventional charge pumps typically generate “up” and “down” currents to control the reference voltage.
A problem with conventional phase locked loops is that the output signals suffer from unwanted spurious signals. These spurious signals can negatively affect the components that use the output signals. For example, communication devices often use phase locked loops to transmit and receive data. Unwanted spurious signals may disturb data being received and introduce unwanted spectral content into data being transmitted.
Charge pumps may often exhibit several different types of problems. For example, charge pumps may operate at slow speeds, have a low output impedance, and generate kick-back noise. It would therefore be advantageous in the art to have an improved charge pump circuit that does not exhibit slow speed, low output impedance, and kick-back noise.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.
The term “controller” means any device, system, or part thereof that controls at least one operation. A controller may be implemented in hardware, software, firmware, or combination thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.
Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as to future uses, of such defined words and phrases.